1991 Chevy C2500 bouncing idle at stop lights

[STS]

Anyone have any idea why my truck will sound like it’s gonna stall at stop lights and low idle then bounce back up and down again? Sounds like it’s running out of gas but that’s not it.

[richard wysong]

Try cleaning the throttle plates and the Idle air control valve. Could be the EGR valve sticking too.

[STS]

Ok I’ll give that a try thankyou

[biscaynekid]

Check for vacuum leaks in hoses, pcv, brake vacuum booster(power brakes).

Booster check: put in neutral and pump brakes. Does idle change?

 

Also, if A/C is on, your idle is supposed to increase. If not, idle will be too low.